Cell Growth & Development: When Do New Cells Form?

1. 10-1 Cell Growth Growth and Development!!

2. When Do New Cells Need to Form? • A. Growth - More cells • B. Maintenance (repair and replacement)--> intestinal lining/RBC’s) • C. Asexual reproduction • D. Formation of sex cells (Meiosis)

3. Limit of cell size? 1. TOO SMALL - There will not be enough room for all the organelles to carry out the processes needed.

4. 2. TOO BIG!: Cell membrane cannot control all movements of materials • The larger a cell grows the more trouble it has… • moving enough nutrients in • Moving all the waste materials out

5. Problem with Being Too Big!! • The volume gets too big for the surface area. • The cell membrane cannot control all the movement in and out when the volume is too large. • Your cells cannot too large either. The surface area must be in the correct ratio of the volume. • Neurons are very long and skinny so that ration is correct.

6. Radius 1cm S.A. = _____ V = ______ Ratio SA:V = ___ Radius 1cm S.A. = __13cm2___ V = __4cm3____ Ratio SA:V = _13:4 or 3.25:1__ Radius 2cm S.A. = ___50cm2__ V = __33cm3____ Ratio SA:V = 50:33_or 1.51:1 Radius 3cm S.A. = _____ V = ______ Ratio SA:V = ___ Radius 3cm S.A. = __113cm2_ V = ___113cm3___ Ratio SA:V = _113:113 or 1:1__ S.A. = 4 (pi) r 2 • As the spheres get larger what happens to the SA:V ratio?

7. 3rd problem: DNA overload

8. 3rd Problem - Too Big 3. DNA overload • Your DNA controls all activities in the cell. When the cell gets too big then the DNA cannot control all activites.

9. Cells Divide at Different Rates • The rate of cell division is determined by the body’s need for that type of cell. • Nerve cells do not divide because they do not die like our skin cells. • A new layer of skin is replaced every 3 weeks. The lining of your intestines has to be replaced often because of the wear and tear. This is also skin cells.

10. The Cell Cycle and Mitosis

11. Cell Cycle – life of a cell • The life of a cell. It has a pattern of cell growth, DNA replication, and cell division. Results in two new daughter cells.

12. The Cell Cycle • The sequence of growth and division of a cell. • 95% of cell cycle in interphase(growth) • 5% of cell cycle in mitosis(division)

13. 3 Main Events of a Cell Cycle 1. Interphase • G1 - growth • S – DNA replication • G2 – growth and prepare for division 2. Mitosis Phase – nucleus dividing • Prophase • Metaphase • Anaphase • Telophase 3. Cytokinesis – cell division

14. What’s Missing?

15. M Phase, Cell Division and Mitosis

16. Cell Cycle • http://www.cellsalive.com/mitosis.htm • http://www.johnkyrk.com/mitosis.html

17. The Cell Cycle - series of events that cells go through as they grow and divide • The cell cycle is divided into two halfs • Interphase - period of the cell cycle between cell divisions • Mitosis phase and cytokinesis – period of time when mitosis and cell division occurs

18. Definitions • Histones • Telomeres • Somatic cells • Chromatin • Chromosomes • Centromeres • Spindle fibers

19. Some Definitions • Histones: proteins that DNA will wrap around. This helps the DNA to fit. • Telomeres: End of DNA molecules to prevent them from attaching to each other. They do not contain genes. • Somatic Cells – body cells • Produced through mitosis • Has 46 chromosomes (23 pairs)

20. Chromatin - A complex of DNA and proteins in the cell nucleus that condenses to form chromosomes during cell division(loose DNA). • Chromosomes – Condensed Chromatin(X) • They are the same stuff, just in different forms • Centromeres: Center point where chromatids are attached. • Spindle Fibers - Fibers that pull part the chromosomes during mitosis.

21. Chromatin Chromosomes Chromatin condenses in chomosomes before mitosis begins

22. Parts of Interphase • G1 Phase(growth) • Cell grows • Synthesize new proteins and organelles • Doing their jobs • Longest phase of cell cycle

23. S Phase • S Phase(synthesis) • Chromosomes(DNA) are replicated • Key proteins associated with replication are made (centromeres

24. Gap 2 Phase • G2 Phase(growth) • Shortest of the 3 phases of interphase • Organelles and molecules for cell division are produced (centrioles) • Check-up phase before mitosis

25. G - 0 Stage This is a stage of interphase that SOME cells enter. Cells such as nerve and white blood do not divide often so they enter this stage of rest.

26. Animated Cycle http://www.cellsalive.com/cell_cycle.htm

28. What stops cell from growing? • Proximity to neighbor cells. • Cells in a petri dish will continue to grow until they come into contact with other cells. • Similarily, skin around a wound After a cell has quit growing, it is time to divide!!! Mitosis

29. MITOSIS

30. Mitosis Division of the nucleus. Followed by cytokinesis!!! The daughter cells are identical to one another and to the original parent cell.

31. Mitosis • Prophase • Metaphase • Anaphase • Telophase

32. Prophase • Longest phase of mitosis • Chromatin condenses into chromosomes • Spindle fibers form and attach to centrioles • Nuclear membrane dissappears • Nucleolus breaks down

34. Prophase Plant Cell Animal Cell Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm

35. Animal Cell Packages DNA into chromosomes Plant cell Packages DNA into chromosomes ProphaseThe cell prepares for nuclear division

36. Metaphase • Centromeres line up across the center of the cell • Spindle fibers connect to centromeres

38. Anaphase • Chromosomes are pulled apart by spindle into individual chromatids. • The chromatids are now considered Chromosomes!!

39. Anaphase • Centromeres split • Sister chromatids are pulled apart to opposite poles of the cell • Each chromatid is now a separate chromosome

42. Telophase • Nuclear envelopes (2) and nucleolus reform • Chromosomes begin to uncoil • Spindle fibers disappear.

43. Mitosis Animation http://www.cellsalive.com/mitosis.htm

44. Animal Mitosis -- Review

45. Plant Mitosis -- Review

46. Cytokinesis • Cytoplasm divides • Two new daughter cellsare now separate

47. http://www.johnkyrk.com/mitosis.html Cytokinesis • The cytoplasm pinches in half • Animal - cleavage furrow • Plants - cell plate

48. In plant cells, a cell plate forms. The cell plate is synthesized by the fusion of multiple membrane-bounded vesicles. Their fusion supplies new plasma membrane for each of the two daughter cells. Synthesis of a new cell wall between the daughter cells then occurs at the cell plate.

49. Apoptosis • Cell death. Factors that signal genes to produce self destructive enzymes. Not sure why. • EX: webbing of toes on an embryo.

50. Cyclins Protein that controls cell division.. They can make cells grow in a petri dish. Doesn’t work on all cells.